Both Steven Moffat and Peter Capaldi give their point of view on the Christmas Special. Here’s what Moffat had to say:

“I’ve always been fascinated by superheroes. Where I think superheroes are at their best is in the secret identity. The most exciting superhero, of all time, is Clark Kent. He has to be a god and pretend he isn’t. It’s the best story ever.”

From what we know right now, the Doctor Who Christmas Special is going to an hour long. The episode will air on Christmas Day 2016.

Synopsis:

The Doctor, played by Peter Capaldi, gets a sidekick in the form of an investigative journalist and a mysterious superhero – collectively teaming up to save New York from a terrible alient attack.